ISBLANK

Function Reference: ISBLANK

Syntax
=ISBLANK(value)
Purpose / Description
Determines if the value is a blank value.
Arguments
Name Type Description
value any The value which is to be examined to determine if it is a blank.
Return Values
Type Specific Value Description
logical TRUE The value argument is blank.
logical FALSE The value argument is not a blank.
Notes / Comments / Advice / Warnings
Note: As this is a function for determining value type, it does not return errors when an error value is passed, as that is not a reference, so in that case, it returns FALSE.
Note: An empty string ("") is not a blank.  Intermediate values returned from lookups and reference formulas can be passed to an ISBLANK function, however, once the result is stored in the cell, it is no longer a blank.
Comment: A lot of users use the comparison to an empty string as a test for blankness, such as =A1="".  This will mostly be correct as the blank cell will be coerced to an empty string to allow the calculation to proceed, but to be completely sure, only =ISBLANK(A1) would be reliable.
Examples: Open / download sample workbook: ISBLANK.xlsx